Method and system for auto wake-up for time lapse image capture in an image capture unit

ABSTRACT

The present invention provides a system and method for timelapse capture in an image capture unit. A system and method for timelapse capture according to the present invention comprises capturing a first image automatically; initiating a sleep mode after capturing the first image; and transitioning from the sleep mode into a wake mode prior to capturing a second image. According to the present invention, a system and method is provided which provides a digital camera with the ability to automatically place the digital camera in a sleep mode during the interval when the camera is inactive. The sleep mode minimizes power consumption during inactive periods of a timelapse capture sequence, thus allowing automation of timelapse sequences. The sleep mode can be initiated if a predetermined time interval is greater than a setup time required prior to initiating the next image capture. The predetermined time interval can be an interval such as a time interval which starts after the end of the processing time required for a first capture and continuing until the second image capture.

CROSS-REFERENCE TO RELATED APPLICATION

This application is related to U.S. Ser. No. 08/918,816, entitled"Method and System of Organizing DMA Transfers to Support ImageRotation." This application is related to U.S. Ser. No. 08/795,587entitled "Apparatus and Method for Camera Image and OrientationCapture," filed Feb. 6, 1997, which is a continuation of U.S. Ser. No.08/384,012 (abandoned), entitled "Apparatus and Method forOrientation-Dependent Camera Exposure and Focus Setting Optimization".Both applications are assigned to the same assignee as the instantapplication.

FIELD OF THE INVENTION

The present invention relates generally to digital image capture units,and more particularly to a method and system for timelapse capture indigital cameras.

BACKGROUND OF THE INVENTION

Most digital cameras today are similar in size to and behave likeconventional point-and-shoot cameras. Unlike conventional cameras,however, most digital cameras store digital images in an internal flashmemory or on external memory cards, and some are equipped with aliquid-crystal display (LCD) screen on the back of the camera. Throughthe use of the LCD, most digital cameras operate in two modes, recordand play, although some only have a record mode. In record mode, the LCDis used as a viewfinder in which the user may view an object or scenebefore taking a picture. In play mode, the LCD is used as a playbackscreen for allowing the user to review previously captured images eitherindividually or in arrays of four, nine, or sixteen images.

One option for which a digital camera can be used is for capturingtimelapse images. Timelapse images typically capture a series of imagesover a period of time. For example, a digital camera can capture variousstages of a rose as it blooms. The user can estimate how long it mighttake the rose to bloom, and capture the image of the rose at periodicintervals during that time. Another example of timelapse image captureis timelapse captures of the growth of a stalk of corn. In thisinstance, the user may choose to capture one or two images per day overseveral days.

Conventional digital cameras typically have no automatic features fortimelapse due to the short life of the battery which is commonly used inthe digital cameras. In live view mode, battery life typically onlylasts 15 to 20 minutes. Thus, the short battery life limits a timelapseseries of image captures to only 15 to 20 minutes, a time which is fartoo short for most timelapse captures.

What is needed is an automatic timelapse capture in an image captureunit, such as a digital camera. The present invention addresses such aneed.

SUMMARY OF THE INVENTION

The present invention provides a system and method for timelapse capturein an image capture unit. A system and method for timelapse captureaccording to the present invention comprises capturing a first imageautomatically; initiating a sleep mode after capturing the first image;and transitioning from the sleep mode into a wake mode prior tocapturing a second image.

According to the present invention, a system and method is providedwhich provides a digital camera with the ability to automatically placethe digital camera in a sleep mode during the interval when the camerais inactive. The sleep mode minimizes power consumption during inactiveperiods of a timelapse capture sequence, thus allowing automation oftimelapse sequences. The sleep mode can be initiated if a predeterminedtime interval is greater than a setup time required prior to initiatingthe next image capture. The predetermined time interval can be aninterval such as a time interval which starts after the end of theprocessing time required for a first capture and continuing until thesecond image capture.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a digital camera in which the presentinvention can reside.

FIG. 2 is a block diagram of an example of an imaging device of FIG. 1.

FIG. 3 is a block diagram of an example of the computer of FIG. 1.

FIG. 4 is a block diagram of a modification of the example of thecomputer shown in FIG. 3 in which the present invention can reside.

FIG. 5 is a timeline illustrating events occurring between the firstcapture and the second capture in a method for automatic timelapsecapture according to the present invention.

FIG. 6 is a flow diagram of the method for automatic timelapse captureaccording to the present invention.

FIG. 7 is a more detailed flow diagram of an embodiment embodying steps612-622 of the method according to the present invention shown in FIG.6.

FIG. 8 is a more detailed flow diagram of another embodiment embodyingsteps 612-622 of the method according to the present invention shown inFIG. 6.

FIG. 9 is a flow diagram of the deep sleep sequence of the methodaccording to the present invention shown in FIG. 8.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a system and method for automatictimelapse capture in an image capture unit. The following description ispresented to enable one of ordinary skill in the arts to make and usethe invention and is provided in the context of a patent application andits requirements. Although the present invention will be described inthe context of a digital camera, various modifications to the preferredembodiment will be readily apparent to those skilled in the art and thegeneric principles herein may be applied to other embodiments. That is,any image capture device could incorporate the features describedhereinbelow and that device would be within the spirit and scope of thepresent invention. Thus, the present invention is not intended to belimited to the embodiment shown, but is to be accorded the widest scopeconsistent with the principles and features described herein.

The present invention is a system and method for timelapse capture whichminimizes power consumption in an image capture unit. According to thepresent invention, a system and method is provided which provides adigital camera with the ability to automatically place the digitalcamera in a sleep mode during the interval when the camera is inactive.The sleep mode minimizes power consumption during inactive periods of atimelapse capture sequence, thus allowing automation of timelapsesequences. The sleep mode can be initiated if a predetermined timeinterval is greater than a setup time required prior to initiating thenext image capture. The predetermined time interval can be an intervalsuch as a time interval which starts after the end of the processingtime required for a first capture and continuing until the second imagecapture.

In operation, a user may set up a digital camera for a timelapsesequence. While setting up the digital camera, the user can indicate atime interval between image captures. After the first image is captured,the digital camera can transition into sleep mode, which minimizes powerconsumption. Thereafter, the camera can transition from sleep mode intoa wake mode prior to the second image capture. Accordingly, thetimelapse capture series can be made automatic without unnecessaryconsumption of battery power.

Referring now to FIG. 1, a block diagram of a digital camera 110 isshown according to the present invention. Camera 110 preferablycomprises an imaging device 114, a system bus 116 and a computer 118.Imaging device 114 is optically coupled to an object 112 andelectrically coupled via system bus 116 to computer 118. Once aphotographer has focused imaging device 114 on object 112 and, using acapture button or some other means, instructed camera 110 to capture animage of object 112, computer 118 commands imaging device 114 via systembus 116 to capture raw image data representing object 112. The capturedraw image data is transferred over system bus 116 to computer 118 whichperforms various image processing functions on the image data beforestoring it in its internal memory. System bus 116 also passes variousstatus and control signals between imaging device 114 and computer 118.

Referring now to FIG. 2, a block diagram of an example of an imagingdevice 114 is shown. Imaging device 114 preferably comprises a lens 220having an iris, a filter 222, an image sensor 224, a timing generator226, an analog signal processor (ASP) 228, an analog-to-digital (A/D)converter 230, an interface 232, and one or more motors 234.

Imaging device 114 captures an image of object 112 via reflected lightimpacting image sensor 224 along optical path 236. Image sensor 224,which is preferably a charged coupled device (CCD), responsivelygenerates a set of raw image data in CCD format representing thecaptured image 112. The raw image data is then routed through ASP 228,A/D converter 230 and interface 232. Interface 232 has outputs forcontrolling ASP 228, motors 234 and timing generator 226. From interface232, the raw image data passes over system bus 116 to computer 118.

Referring now to FIG. 3, a block diagram of an example of computer 118is shown. System bus 116 provides connection paths between imagingdevice 114, an optional power manager 342, central processing unit (CPU)344, dynamic random-access memory (DRAM) 346, input/output interface(I/O) 348, non-volatile memory 350, and buffers/connector 352. Removablememory 354 connects to system bus 116 via buffers/connector 352.Alternately, camera 110 may be implemented without removable memory 354or buffers/connector 352.

Power manager 342 communicates via line 366 with power supply 356 andcoordinates power management operations for camera 110. CPU 344typically includes a conventional processor device for controlling theoperation of camera 110. In the preferred embodiment, CPU 344 is capableof concurrently running multiple software routines to control thevarious processes of camera 110 within a multi-threading environment.DRAM 346 is a contiguous block of dynamic memory which may beselectively allocated to various storage functions. LCD controller 390accesses DRAM 346 and transfers processed image data to LCD screen 402for display.

I/O 348 is an interface device allowing communications to and fromcomputer 118. For example, I/O 348 permits an external host computer(not shown) to connect to and communicate with computer 118. I/O 348also interfaces with a plurality of buttons and/or dials 404, and anoptional status LCD 406, which in addition to the LCD screen 402, arethe hardware elements of the camera's user interface 408.

Non-volatile memory 350, which may typically comprise a conventionalread-only memory or flash memory, stores a set of computer-readableprogram instructions to control the operation of camera 110. Removablememory 354 serves as an additional image data storage area and ispreferably a non-volatile device, readily removable and replaceable by acamera 110 user via buffers/connector 352. Thus, a user who possessesseveral removable memories 354 may replace a full removable memory 354with an empty removable memory 354 to effectively expand thepicture-taking capacity of camera 110. Removable memory 354 can beimplemented by using a flash disk.

Power supply 356 supplies operating power to the various components ofcamera 110. The power supply 356 provides operating power to a mainpower bus 362 and also to a secondary power bus 364. The main power bus362 provides power to imaging device 114, I/O 348, non-volatile memory350 and removable memory 354. The secondary power bus 364 provides powerto power manager 342, CPU 344 and DRAM 346.

Power supply 356 is connected to main batteries 358 and also to backupbatteries 360. In the preferred embodiment, a camera 110 user may alsoconnect power supply 356 to an external power source. During normaloperation of power supply 356, the main batteries 358 provide operatingpower to power supply 356 which then provides the operating power tocamera 110 via both main power bus 362 and secondary power bus 364.During a power failure mode in which the main batteries 358 have failed(when their output voltage has fallen below a minimum operationalvoltage level) the backup batteries 360 provide operating power to powersupply 356 which then provides the operating power only to the secondarypower bus 364 of camera 110.

FIG. 4 is a block diagram showing further details of the general blockdiagram of the computer system shown in FIG. 3 according to the presentinvention. The system of FIG. 4 includes a main battery 358' working inconjunction with a main power supply 356'. An optional backup battery360' can also be included to work in conjunction with a backup powersupply 361'. A power manager 342' works in conjunction with the mainpower supply 356'. The power manager 342' is coupled to the CPU 344' andis supplied with power by the backup supply.

A timer or a real time clock (RTC) 402 is shown included in the CPU344'. Alternatively, the timer 402 can be included in the power manager342'. The RAM 346', the ROM or flash memory 350', and the input/output(I/O) 348' are also shown to be included within the system of FIG. 4.The remaining system is unchanged from that shown in FIG. 3.

Various signals are communicated between the timer 402 and the powermanager 342'. For instance, the system of FIG. 4 is shown to have keepalive power (KAPWR) 400 from the backup supply and a wakeup signal 404communicating between the timer 402 and the power manager 342'. TheKAPWR signal is a power input to keep the real time clock running. Areset signal 406 and an interrupt signal 408 are also shown to becommunicated between the power manager 342' and the CPU 344'.

The system according to the present invention also permits the option ofhaving a normal operation mode or a sleep mode, as shown by area 410.Area 410 includes a switch 412 which can switch between normal operationmode and sleep mode. The switch 412 is an electrical switch and iscontrolled by the power manager 342'. The electrical switch 412 can be,for example, a dual back-to-back field effect transistor (FET) betweenthe main power bus 362 on the backup power bus 363. Sleep mode, as meantherein, generally refers to any mode which utilizes less than fullbattery power, but preferably utilizes the battery power such that theaveraged power throughout the timelapse sequence is minimized.

FIG. 5 is a timing diagram of events occurring between a first imagecapture and a second image capture. In this timing diagram 500, a firstimage capture is taken at 502. Thereafter, the first image is processedduring processing time 504. The processing time 504 is expected to rangeapproximately 0.5-2.0 seconds for a hardware based camera and 2-30seconds for a software based camera. A capture interval 506 is the timeinterval between two consecutive image captures. Within the captureinterval 506, the processing time 504, a sleep interval 508 and a setuptime 514 are included. The sleep interval 508 and the setup time 514 areseparated by the wakeup event 520. The setup time 514 can be acompilation of various other times such as startup time 510 and strobecharge time 512. Note the strobe charge time 512 is optional dependingon whether a strobe is used for capture. Additionally, the strobe chargetime 512 and the startup time 510 can occur simultaneously. Since strobecharge time 512 will typically be longer than the startup time 510, itis preferable for the strobe charge time 512 to begin before the startuptime 510 is initiated. The strobe charge time 512 (i.e., the time forthe strobe to charge) can range approximately 2-8 seconds. Often, thestrobe charge time 512 may be unnecessary since a strobe may not beused. When a strobe is not used, then only the startup time 510 will beinitiated. The various time intervals depend on factory settings and canvary widely.

One way of reducing power during a time lapse image capture sequence isto shut off all circuitry related to capturing after an image has beencaptured until the initiation of the next setup time. Additionally, thesetting of the image camera lenses can simply remain the same as whenthe camera is set for the first image. For example, in an image captureunit which withdraws its lenses when the image capture unit is shut off,during sleep mode lenses would remain in the same position as they arein capture mode.

FIG. 6 is a flow diagram of a method for automatic timelapse capture inan image capture unit according to the present invention. The method ofFIG. 6 can be viewed in light of the timeline 500 of FIG. 5. The methodof FIG. 6 initiates with a setup phase 600. During the setup phase, theuser can establish information regarding the timelapse capture series,such as the image count, the capture interval, explicit/implicit lock,determine strobe or flash, and physical setup of the digital camera. Theimage count is a determination of how many total number of images thedigital camera should take during the timelapse series. A captureinterval is the time interval between two consecutive image captures.Explicit/implicit lock relates to a determination of whether theexposure is locked, i.e., whether the digital camera adjusts to changesin the light. The physical setup can include placing the digital cameraupon a tripod, pointed in the desired angle at the object.

The shutter button can then be pressed, via step 602. Usually, pressingthe shutter button will initiate the first image capture. The image isthen processed, via step 604. It is then determined whether the captureinterval is greater than the sum of the setup time and the processingtime, via step 606. The capture interval 506, the processing time 504,and the setup time 514 are shown in FIG. 5.

If the capture interval 506 is not greater than the sum of theprocessing time 504 and the setup time 514, via step 606 of FIG. 6, thenthe digital camera system waits until time for the next image capture,via step 616. If, however, the capture interval 506 is greater than thesetup time 514, via step 606, then sleep mode is initiated via step 608.The term "sleep mode", as before mentioned, is herein referred to meanany state which utilizes less than full power. For example, the Motorolaprocessor MTC823 utilizes terms indicating ranges of required power.These terms include full, doze, sleep, deep sleep, power down, and poweroff. These terms are listed in the order of higher power required tolower power required. The lower the power, the longer and more complexthe start/stop routine of the system. Although processors, such as theMotorola processor MTC823, provide power management capability in thehardware, the power management capability had not been utilized inworking in conjunction with time lapse image capturing in image captureunits such as digital cameras because external circuitry, such as forthe power manager, and complex software are required to do so.

Again, anything less than full power is generally referred to herein as"sleep mode". The preferred state of sleep mode is either deep sleep orpower down, depending on software and hardware capacities. "Power down"implies all power being off except for the realtime clock, some startupcircuitry, and power up circuitry, depending on the chip manufacturer.If the digital camera system 10 reduces power to the "power off" state,however, the system may have to be rebooted which consumes power.Reducing power to deep sleep, however, does not require a reboot of thedigital camera. Examples of how long it would take to wake up from asleep state may be 5 seconds to wake up from a power down, and 0.5seconds to wake up from deep sleep. Although deep sleep continuouslydraws power, the typical timelapse selected between image captures isshort enough to make it efficient to avoid rebooting.

If the capture interval 506 is greater than the sum of the processingtime 504 and the setup time 514, via step 606 of FIG. 6, sleep isinitiated via step 608. After sleep has been initiated, there is awaiting period which is equivalent to the sleep interval 508 (FIG. 5),via step 610. After the sleep interval 508, the digital camera systemwakes up, via step 612. After waking up, the digital camera system setsup for the next capture, via step 614. The next capture is then taken,via step 618. It is then determined if the capture taken in step 618 wasthe last capture, via step 620. If the capture was not the last capture,then the image is processed via step 604 and it is determined if thecapture interval is greater than the setup time, via step 606. If,however, the capture of step 618 was the last capture, then the image isprocessed via step 622 and the sequence is ended.

FIG. 7 is a more detailed flow diagram of an embodiment of the automatictimelapse capture which occurs between wake-up (step 612) and imageprocessing (step 622) of FIG. 6. Wake-up is initiated when atimeout-startup signal is received via step 700 from the timer 402 shownin FIG. 4. The power supply is started, via step 702. The system thenwaits for the stabilization of the power supply, via step 704. Theprocessor is reset via step 706, and the processor boots via step 708.It is then determined what caused the wakeup, via step 710. If somethingother than the timer, such as the user, caused the wakeup, it is thendetermined whether the digital camera is in the middle of performing atimelapse sequence, via step 716. Step 716 can be determined bydetermining whether the timer is running. If a timelapse sequence is notbeing performed, then normal operations can proceed. If, however, atimelapse sequence is being performed, then the timelapse state isretrieved, via step 712.

Likewise, if the timer caused the wakeup via step 710, then thetimelapse state is retrieved, via step 712. The timelapse is thencontinued, via step 714. Once an image is captured, and it is determinedthat that capture is not the last image via step 733, then a nonvolatilememory is set, via step 724. The nonvolatile memory is set to storeinformation regarding the time lapse capture series. The information caninclude, for example, how many images have been taken in the series, howmany images are yet to be taken, what is the time interval, locationwhere images in a series are to be stored, and all camera settings.After the nonvolatile memory is set then a normal timelapse shutdown isperformed, via step 730, i.e., sleep is initiated.

If the last image is captured, via step 733, and the processing iscomplete, then the nonvolatile memory is cleared and normal shutdown isperformed, via step 722. Normal shutdown can include a period of sleepmode followed by power-off, or simply power-off.

If the digital camera is powered down by the user, then it is determinedwhether there is enough time left before the next capture, via step 720.If there is not time left before the next capture to sleep, then awarning is displayed for the user via step 728 and step 714 continues.Note that the user can abort the time-lapse sequence during step 714.Otherwise, the timelapse program is shut down via step 724.

If it is determined to abort the timelapse sequence, then timelapsesequence is exited and non-volatile memory is cleared via step 732.

FIG. 8 is a detailed flow diagram of another embodiment embodying thesteps of 612-622 shown in FIG. 6. While the embodiment shown in FIG. 7boots the processor, the embodiment shown in FIG. 8 simply interruptsthe CPU. Wake-up is initiated when a timeout-startup signal is receivedvia step 800 from the timer 402 shown in FIG. 4. The power supply isstarted, via step 802. The system then waits for the stabilization ofthe power supply, via step 804. The CPU is then interrupted via step808, and DRAM is restored to normal load via step 810.

It is then determined what caused the wakeup, via step 812. If somethingother than the timer, such as the user, caused the wakeup, it is thendetermined whether the digital camera is in the middle of performing atimelapse sequence, via step 816. Step 816 can be determined bydetermining whether the timer is running. If a timelapse sequence is notbeing performed, then normal operations can proceed. If, however, atimelapse sequence is being performed, then the timelapse state isretrieved, via step 814.

Likewise, if the timer caused the wakeup via step 812, then thetimelapse state is retrieved, via step 814. The timelapse is thencontinued, via step 818. Once an image is captured, and it is determinedthat that capture is not the last image via step 833, then a normaltimelapse shutdown is performed via step 824, i.e., sleep is initiated.A deep sleep sequence is initiated via step 828.

If the last image is captured via step 833, and the processing iscomplete, then normal shutdown is performed, via step 822. Normalshutdown can include a period of sleep mode followed by power-off, orsimply power-off.

If the digital camera is powered down by the user, then it is determinedwhether there is enough time left before the next capture, via step 826.If there is not time left before the next capture to sleep, then awarning is displayed for the user via step 832 and step 818 continues.Note that the user can abort the time-lapse sequence during step 818.Otherwise, the normal timelapse shut down is performed via step 830, anddeep sleep sequence is initiated via step 828.

If it is determined to abort the timelapse sequence, then timelapsesequence is exited via step 834.

FIG. 9 is a flow diagram of the deep sleep sequence 828 shown in FIG. 8.When deep sleep is initiated, deep sleep instructions are loaded, forinstance into a cache, via step 900, because commands cannot be executedfrom the ROM until main power is restored. The DRAM is placed into selfrefresh (SR) mode, via step 902. The CPU signals the power manager tosleep, via step 904. The CPU then halts, waiting for an interrupt, viastep 906. The digital camera system is then switched back to backuppower via step 908, and the main power supply is then shut off, via step910.

A method and system for automatic timelapse capture in an image captureunit has been disclosed. Software written according to the presentinvention is to be stored in some form of computer-readable medium, suchas memory or CD-ROM, or transmitted over a network, and executed by aprocessor.

Although the present invention has been described in accordance with theembodiments shown, one of ordinary skill in the art will readilyrecognize that there could be variations to the embodiments and thosevariations would be within the spirit and scope of the presentinvention. Accordingly, many modifications may be made by one ofordinary skill in the art without departing from the spirit and scope ofthe appended claims.

What is claimed is:
 1. A method for time lapse capture in an imagecapture unit, the method comprising:allowing the image capture unit tobe placed in a time lapse sequence; capturing a first image;automatically initiating a sleep mode after capturing the first image ifthe image capture unit is in the time lapse sequence; and automaticallytransitioning from the sleep mode into a wake mode prior to capturing asecond image if the image capture device is in the time lapse sequence.2. The method of claim 1, wherein the sleep mode is initiated when apredetermined time interval is greater than a sum of a processing timeand a setup time.
 3. The method of claim 1, wherein the sleep mode isnot initiated when a predetermined time interval is not greater than asum of a processing time and a setup time.
 4. The method of claim 1,wherein the step of transitioning further includes booting up aprocessor.
 5. The method of claim 1, further comprising a step ofdetermining whether the time lapse sequence is being performed after thestep of transitioning.
 6. The method of claim 1, wherein the step oftransitioning further includes restoring a memory to normal operation.7. The method of claim 1, wherein the sleep mode is a deep sleep.
 8. Amethod for time lapse capture in an image capture unit, the methodcomprising:allowing the image capture unit to be placed in a time lapsesequence; determining if a predetermined time interval is greater than asum of a processing time and setup time, the predetermined intervalbeing a capture interval; automatically initiating a sleep mode if thepredetermined time interval is greater than the sum of the processingtime and the setup time and if the image capture unit is in the timelapse sequence; and automatically transitioning from the sleep mode to awake up mode prior to capturing an image if the image capture device isin the time lapse sequence.
 9. The method of claim 8, further comprisinga step of capturing a first image prior to the step of determining. 10.The method of claim 8, wherein the sleep mode is not initiated when apredetermined time interval is not greater than a sum of a processingtime and a setup time.
 11. The method of claim 8, wherein the step oftransitioning further includes booting up a processor.
 12. The method ofclaim 8, further comprising a step of determining whether the time lapsesequence is being performed after the step of transitioning.
 13. Themethod of claim 8, wherein the step of transitioning further includesrestoring a memory to normal load.
 14. The method of claim 8, whereinthe sleep mode is a deep sleep.
 15. A system for time lapse capture inan image capture unit, the system comprising:a processor; a timercoupled to the processor, the timer notifying the processor when apredetermined time interval has completed prior to an image capture; anda switch coupled to the processor, the switch operating in one of twomodes, wherein a first mode is a normal operation mode, and a secondmode is a sleep mode; wherein the switch automatically transitions fromthe first mode to the second mode after the image capture is completedif the image capture unit is in a time lapse sequence and automaticallytransitions from the second mode to the first mode when thepredetermined time interval has completed if the image capture unit isin the time lapse sequence.
 16. The system of claim 15, furthercomprising a power manager coupled to the processor and the timer,wherein the timer sends a signal to the power manager notifying thepower manager that the predetermined time interval has completed. 17.The system of claim 15, wherein the processor determines if thepredetermined time interval is greater than a sum of a processing timeand a setup time.
 18. The system of claim 17, wherein the switchoperates in the sleep mode if the predetermined time interval is greaterthan the sum of the processing time and the setup time.
 19. The systemof claim 17, wherein the sleep mode is not initiated when thepredetermined time interval is not greater than the sum of theprocessing time and the setup time.
 20. The system of claim 17, whereinthe processor boots up when the switch transitions from the second modeto the first mode.
 21. The system of claim 17, wherein the a memory isrestored to normal load when the switch transitions from the second modeto the first mode.
 22. The system of claim 17, wherein the sleep mode isa deep sleep.